Liquid coolers are used to provide accessory liquid cooling to a wide variety of vehicle and system components. Essentially, liquid coolers consist of fluid tubes coupled to a vehicle or system component. The outer surfaces of the fluid tubes provide a surface to remove heat from the vehicle or system component.
In general, liquid flowing through the tubing experiences laminar flow, turbulent flow, or a combination of laminar and turbulent flow. In the context of liquid coolers, laminar flow is fluid flow in which all fluid motion is in the direction of the axis of the tubing, while turbulent flow is fluid flow in which the fluid is tumbling or mixing within the tube.
Consider laminar flow, for example, in a horizontally oriented simple plain tube having a one-half inch diameter and one meter long having diesel flow entering the tube at a bulk flow rate of 0.5 liters per minute and wherein 50 watts is applied evenly to the tubing wall. Where the bulk inlet diesel fuel temperature is fifty degrees Celsius, the bulk outlet diesel fuel temperature will be 53 degrees Celsius. The temperature along the tubing wall, and the diesel fuel very close to the tubing wall, is 76 degrees, or 24.5 degrees hotter than the average fluid temperature. This demonstrates that the temperature rise within the fluid from the bulk of the fluid to the inside wall of the tubing dominates the total temperature rise. As the amount of heat that a liquid cooler is able to remove is proportional to the temperature difference between the the tubing wall surface and fluid and to the surface area of the tubing available to the fluid, liquid coolers in the present art incorporate expensive u-bends in their designs to increase the surface area and overcome the low convection performance ability of the tubing.
It is therefore highly desirable to limit the temperature rise between the inside wall of a tubing and a liquid flowing through the tubing at a constant flow rate. This would increase the thermal effectiveness of the liquid cooler for cooling an associated component. This would also allow liquid coolers to be formed with decreased sizes while limiting or eliminating expensive u-bends that are normally necessary to provide adequate cooling to an associated component.